kingst-la2016: comment on FPGA register at offset 0x0004 (unused)

[libsigrok.git] / src / hardware / kingst-la2016 / protocol.c

/*
 * This file is part of the libsigrok project.
 *
 * Copyright (C) 2022 Gerhard Sittig <gerhard.sittig@gmx.net>
 * Copyright (C) 2020 Florian Schmidt <schmidt_florian@gmx.de>
 * Copyright (C) 2013 Marcus Comstedt <marcus@mc.pp.se>
 * Copyright (C) 2013 Bert Vermeulen <bert@biot.com>
 * Copyright (C) 2012 Joel Holdsworth <joel@airwebreathe.org.uk>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <config.h>

#include <libsigrok/libsigrok.h>
#include <string.h>

#include "libsigrok-internal.h"
#include "protocol.h"

/* USB PID dependent MCU firmware. Model dependent FPGA bitstream. */
#define MCU_FWFILE_FMT  "kingst-la-%04x.fw"
#define FPGA_FWFILE_FMT "kingst-%s-fpga.bitstream"

/*
 * List of supported devices and their features. See @ref kingst_model
 * for the fields' type and meaning. Table is sorted by EEPROM magic.
 *
 * TODO
 * - Below LA1016 properties were guessed, need verification.
 * - Add LA5016 and LA5032 devices when their EEPROM magic is known.
 * - Does LA1010 fit the driver implementation? Samplerates vary with
 *   channel counts, lack of local sample memory. Most probably not.
 */
static const struct kingst_model models[] = {
        { 2, "LA2016", "la2016", SR_MHZ(200), 16, 1, },
        { 3, "LA1016", "la1016", SR_MHZ(100), 16, 1, },
        { 8, "LA2016", "la2016a1", SR_MHZ(200), 16, 1, },
        { 9, "LA1016", "la1016a1", SR_MHZ(100), 16, 1, },
};

/* USB vendor class control requests, executed by the Cypress FX2 MCU. */
#define CMD_FPGA_ENABLE 0x10
#define CMD_FPGA_SPI    0x20    /* R/W access to FPGA registers via SPI. */
#define CMD_BULK_START  0x30    /* Start sample data download via USB EP6 IN. */
#define CMD_BULK_RESET  0x38    /* Flush FIFO of FX2 USB EP6 IN. */
#define CMD_FPGA_INIT   0x50    /* Used before and after FPGA bitstream upload. */
#define CMD_KAUTH       0x60    /* Communicate to auth IC (U10). Not used. */
#define CMD_EEPROM      0xa2    /* R/W access to EEPROM content. */

/*
 * FPGA register addresses (base addresses when registers span multiple
 * bytes, in that case data is kept in little endian format). Passed to
 * CMD_FPGA_SPI requests. The FX2 MCU transparently handles the detail
 * of SPI transfers encoding the read (1) or write (0) direction in the
 * MSB of the address field. There are some 60 byte-wide FPGA registers.
 *
 * Unfortunately the FPGA registers change their meaning between the
 * read and write directions of access, or exclusively provide one of
 * these directions and not the other. This is an arbitrary vendor's
 * choice, there is nothing which the sigrok driver could do about it.
 * Values written to registers typically cannot get read back, neither
 * verified after writing a configuration, nor queried upon startup for
 * automatic detection of the current configuration. Neither appear to
 * be there echo registers for presence and communication checks, nor
 * version identifying registers, as far as we know.
 */
#define REG_RUN         0x00    /* Read capture status, write start capture. */
#define REG_PWM_EN      0x02    /* User PWM channels on/off. */
#define REG_CAPT_MODE   0x03    /* Write 0x00 capture to SDRAM, 0x01 streaming. */
#define REG_PIN_STATE   0x04    /* Read current pin state (real time display). */
#define REG_BULK        0x08    /* Write start addr, byte count to download samples. */
#define REG_SAMPLING    0x10    /* Write capture config, read capture SDRAM location. */
#define REG_TRIGGER     0x20    /* Write level and edge trigger config. */
#define REG_UNKNOWN_30  0x30
#define REG_THRESHOLD   0x68    /* Write PWM config to setup input threshold DAC. */
#define REG_PWM1        0x70    /* Write config for user PWM1. */
#define REG_PWM2        0x78    /* Write config for user PWM2. */

/* Bit patterns to write to REG_CAPT_MODE. */
#define CAPTMODE_TO_RAM 0x00
#define CAPTMODE_STREAM 0x01

/* Bit patterns to write to REG_RUN, setup run mode. */
#define RUNMODE_HALT    0x00
#define RUNMODE_RUN     0x03

/* Bit patterns when reading from REG_RUN, get run state. */
#define RUNSTATE_IDLE_BIT       (1UL << 0)
#define RUNSTATE_DRAM_BIT       (1UL << 1)
#define RUNSTATE_TRGD_BIT       (1UL << 2)
#define RUNSTATE_POST_BIT       (1UL << 3)

static int ctrl_in(const struct sr_dev_inst *sdi,
        uint8_t bRequest, uint16_t wValue, uint16_t wIndex,
        void *data, uint16_t wLength)
{
        struct sr_usb_dev_inst *usb;
        int ret;

        usb = sdi->conn;

        ret = libusb_control_transfer(usb->devhdl,
                LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_ENDPOINT_IN,
                bRequest, wValue, wIndex, data, wLength,
                DEFAULT_TIMEOUT_MS);
        if (ret != wLength) {
                sr_dbg("USB ctrl in: %d bytes, req %d val %#x idx %d: %s.",
                        wLength, bRequest, wValue, wIndex,
                        libusb_error_name(ret));
                sr_err("Cannot read %d bytes from USB: %s.",
                        wLength, libusb_error_name(ret));
                return SR_ERR_IO;
        }

        return SR_OK;
}

static int ctrl_out(const struct sr_dev_inst *sdi,
        uint8_t bRequest, uint16_t wValue, uint16_t wIndex,
        void *data, uint16_t wLength)
{
        struct sr_usb_dev_inst *usb;
        int ret;

        usb = sdi->conn;

        ret = libusb_control_transfer(usb->devhdl,
                LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_ENDPOINT_OUT,
                bRequest, wValue, wIndex, data, wLength,
                DEFAULT_TIMEOUT_MS);
        if (ret != wLength) {
                sr_dbg("USB ctrl out: %d bytes, req %d val %#x idx %d: %s.",
                        wLength, bRequest, wValue, wIndex,
                        libusb_error_name(ret));
                sr_err("Cannot write %d bytes to USB: %s.",
                        wLength, libusb_error_name(ret));
                return SR_ERR_IO;
        }

        return SR_OK;
}

/* HACK Experiment to spot FPGA registers of interest. */
static void la2016_dump_fpga_registers(const struct sr_dev_inst *sdi,
        const char *caption, size_t reg_lower, size_t reg_upper)
{
        static const size_t dump_chunk_len = 16;

        size_t rdlen;
        uint8_t rdbuf[0x80 - 0x00];     /* Span all FPGA registers. */
        const uint8_t *rdptr;
        int ret;
        size_t dump_addr, indent, dump_len;
        GString *txt;

        if (sr_log_loglevel_get() < SR_LOG_SPEW)
                return;

        if (!reg_lower && !reg_upper) {
                reg_lower = 0;
                reg_upper = sizeof(rdbuf);
        }
        if (reg_upper - reg_lower > sizeof(rdbuf))
                reg_upper = sizeof(rdbuf) - reg_lower;

        rdlen = reg_upper - reg_lower;
        ret = ctrl_in(sdi, CMD_FPGA_SPI, reg_lower, 0, rdbuf, rdlen);
        if (ret != SR_OK) {
                sr_err("Cannot get registers space.");
                return;
        }
        rdptr = rdbuf;

        sr_spew("FPGA registers dump: %s", caption ? : "for fun");
        dump_addr = reg_lower;
        while (rdlen) {
                dump_len = rdlen;
                indent = dump_addr % dump_chunk_len;
                if (dump_len > dump_chunk_len)
                        dump_len = dump_chunk_len;
                if (dump_len + indent > dump_chunk_len)
                        dump_len = dump_chunk_len - indent;
                txt = sr_hexdump_new(rdptr, dump_len);
                sr_spew("  %04zx  %*s%s",
                        dump_addr, (int)(3 * indent), "", txt->str);
                sr_hexdump_free(txt);
                dump_addr += dump_len;
                rdptr += dump_len;
                rdlen -= dump_len;
        }
}

/*
 * Check the necessity for FPGA bitstream upload, because another upload
 * would take some 600ms which is undesirable after program startup. Try
 * to access some FPGA registers and check the values' plausibility. The
 * check should fail on the safe side, request another upload when in
 * doubt. A positive response (the request to continue operation with the
 * currently active bitstream) should be conservative. Accessing multiple
 * registers is considered cheap compared to the cost of bitstream upload.
 *
 * It helps though that both the vendor software and the sigrok driver
 * use the same bundle of MCU firmware and FPGA bitstream for any of the
 * supported models. We don't expect to successfully communicate to the
 * device yet disagree on its protocol. Ideally we would access version
 * identifying registers for improved robustness, but are not aware of
 * any. A bitstream reload can always be forced by a power cycle.
 */
static int check_fpga_bitstream(const struct sr_dev_inst *sdi)
{
        uint8_t init_rsp;
        uint8_t buff[REG_PWM_EN - REG_RUN]; /* Larger of REG_RUN, REG_PWM_EN. */
        int ret;
        uint16_t run_state;
        uint8_t pwm_en;
        size_t read_len;
        const uint8_t *rdptr;

        sr_dbg("Checking operation of the FPGA bitstream.");
        la2016_dump_fpga_registers(sdi, "bitstream check", 0, 0);

        init_rsp = ~0;
        ret = ctrl_in(sdi, CMD_FPGA_INIT, 0x00, 0, &init_rsp, sizeof(init_rsp));
        if (ret != SR_OK || init_rsp != 0) {
                sr_dbg("FPGA init query failed, or unexpected response.");
                return SR_ERR_IO;
        }

        read_len = sizeof(run_state);
        ret = ctrl_in(sdi, CMD_FPGA_SPI, REG_RUN, 0, buff, read_len);
        if (ret != SR_OK) {
                sr_dbg("FPGA register access failed (run state).");
                return SR_ERR_IO;
        }
        rdptr = buff;
        run_state = read_u16le_inc(&rdptr);
        sr_spew("FPGA register: run state 0x%04x.", run_state);
        if (run_state && (run_state & 0x3) != 0x1) {
                sr_dbg("Unexpected FPGA register content (run state).");
                return SR_ERR_DATA;
        }
        if (run_state && (run_state & ~0xf) != 0x85e0) {
                sr_dbg("Unexpected FPGA register content (run state).");
                return SR_ERR_DATA;
        }

        read_len = sizeof(pwm_en);
        ret = ctrl_in(sdi, CMD_FPGA_SPI, REG_PWM_EN, 0, buff, read_len);
        if (ret != SR_OK) {
                sr_dbg("FPGA register access failed (PWM enable).");
                return SR_ERR_IO;
        }
        rdptr = buff;
        pwm_en = read_u8_inc(&rdptr);
        sr_spew("FPGA register: PWM enable 0x%02x.", pwm_en);
        if ((pwm_en & 0x3) != 0x0) {
                sr_dbg("Unexpected FPGA register content (PWM enable).");
                return SR_ERR_DATA;
        }

        sr_info("Could re-use current FPGA bitstream. No upload required.");
        return SR_OK;
}

static int upload_fpga_bitstream(const struct sr_dev_inst *sdi,
        const char *bitstream_fname)
{
        struct drv_context *drvc;
        struct sr_usb_dev_inst *usb;
        struct sr_resource bitstream;
        uint32_t bitstream_size;
        uint8_t buffer[sizeof(uint32_t)];
        uint8_t *wrptr;
        uint8_t block[4096];
        int len, act_len;
        unsigned int pos;
        int ret;
        unsigned int zero_pad_to;

        drvc = sdi->driver->context;
        usb = sdi->conn;

        sr_info("Uploading FPGA bitstream '%s'.", bitstream_fname);

        ret = sr_resource_open(drvc->sr_ctx, &bitstream,
                SR_RESOURCE_FIRMWARE, bitstream_fname);
        if (ret != SR_OK) {
                sr_err("Cannot find FPGA bitstream %s.", bitstream_fname);
                return ret;
        }

        bitstream_size = (uint32_t)bitstream.size;
        wrptr = buffer;
        write_u32le_inc(&wrptr, bitstream_size);
        ret = ctrl_out(sdi, CMD_FPGA_INIT, 0x00, 0, buffer, wrptr - buffer);
        if (ret != SR_OK) {
                sr_err("Cannot initiate FPGA bitstream upload.");
                sr_resource_close(drvc->sr_ctx, &bitstream);
                return ret;
        }
        zero_pad_to = bitstream_size;
        zero_pad_to += LA2016_EP2_PADDING - 1;
        zero_pad_to /= LA2016_EP2_PADDING;
        zero_pad_to *= LA2016_EP2_PADDING;

        pos = 0;
        while (1) {
                if (pos < bitstream.size) {
                        len = (int)sr_resource_read(drvc->sr_ctx, &bitstream,
                                block, sizeof(block));
                        if (len < 0) {
                                sr_err("Cannot read FPGA bitstream.");
                                sr_resource_close(drvc->sr_ctx, &bitstream);
                                return SR_ERR_IO;
                        }
                } else {
                        /*  Zero-pad until 'zero_pad_to'. */
                        len = zero_pad_to - pos;
                        if ((unsigned)len > sizeof(block))
                                len = sizeof(block);
                        memset(&block, 0, len);
                }
                if (len == 0)
                        break;

                ret = libusb_bulk_transfer(usb->devhdl, USB_EP_FPGA_BITSTREAM,
                        &block[0], len, &act_len, DEFAULT_TIMEOUT_MS);
                if (ret != 0) {
                        sr_dbg("Cannot write FPGA bitstream, block %#x len %d: %s.",
                                pos, (int)len, libusb_error_name(ret));
                        ret = SR_ERR_IO;
                        break;
                }
                if (act_len != len) {
                        sr_dbg("Short write for FPGA bitstream, block %#x len %d: got %d.",
                                pos, (int)len, act_len);
                        ret = SR_ERR_IO;
                        break;
                }
                pos += len;
        }
        sr_resource_close(drvc->sr_ctx, &bitstream);
        if (ret != SR_OK)
                return ret;
        sr_info("FPGA bitstream upload (%" PRIu64 " bytes) done.",
                bitstream.size);

        return SR_OK;
}

static int enable_fpga_bitstream(const struct sr_dev_inst *sdi)
{
        int ret;
        uint8_t resp;

        ret = ctrl_in(sdi, CMD_FPGA_INIT, 0x00, 0, &resp, sizeof(resp));
        if (ret != SR_OK) {
                sr_err("Cannot read response after FPGA bitstream upload.");
                return ret;
        }
        if (resp != 0) {
                sr_err("Unexpected FPGA bitstream upload response, got 0x%02x, want 0.",
                        resp);
                return SR_ERR_DATA;
        }
        g_usleep(30 * 1000);

        ret = ctrl_out(sdi, CMD_FPGA_ENABLE, 0x01, 0, NULL, 0);
        if (ret != SR_OK) {
                sr_err("Cannot enable FPGA after bitstream upload.");
                return ret;
        }
        g_usleep(40 * 1000);

        return SR_OK;
}

static int set_threshold_voltage(const struct sr_dev_inst *sdi, float voltage)
{
        int ret;
        uint16_t duty_R79, duty_R56;
        uint8_t buf[REG_PWM1 - REG_THRESHOLD]; /* Width of REG_THRESHOLD. */
        uint8_t *wrptr;

        /* Clamp threshold setting to valid range for LA2016. */
        if (voltage > LA2016_THR_VOLTAGE_MAX) {
                voltage = LA2016_THR_VOLTAGE_MAX;
        } else if (voltage < -LA2016_THR_VOLTAGE_MAX) {
                voltage = -LA2016_THR_VOLTAGE_MAX;
        }

        /*
         * Two PWM output channels feed one DAC which generates a bias
         * voltage, which offsets the input probe's voltage level, and
         * in combination with the FPGA pins' fixed threshold result in
         * a programmable input threshold from the user's perspective.
         * The PWM outputs can be seen on R79 and R56 respectively, the
         * frequency is 100kHz and the duty cycle varies. The R79 PWM
         * uses three discrete settings. The R56 PWM varies with desired
         * thresholds and depends on the R79 PWM configuration. See the
         * schematics comments which discuss the formulae.
         */
        if (voltage >= 2.9) {
                duty_R79 = 0;           /* PWM off (0V). */
                duty_R56 = (uint16_t)(302 * voltage - 363);
        } else if (voltage > -0.4) {
                duty_R79 = 0x00f2;      /* 25% duty cycle. */
                duty_R56 = (uint16_t)(302 * voltage + 121);
        } else {
                duty_R79 = 0x02d7;      /* 72% duty cycle. */
                duty_R56 = (uint16_t)(302 * voltage + 1090);
        }

        /* Clamp duty register values to sensible limits. */
        if (duty_R56 < 10) {
                duty_R56 = 10;
        } else if (duty_R56 > 1100) {
                duty_R56 = 1100;
        }

        sr_dbg("Set threshold voltage %.2fV.", voltage);
        sr_dbg("Duty cycle values: R56 0x%04x, R79 0x%04x.", duty_R56, duty_R79);

        wrptr = buf;
        write_u16le_inc(&wrptr, duty_R56);
        write_u16le_inc(&wrptr, duty_R79);

        ret = ctrl_out(sdi, CMD_FPGA_SPI, REG_THRESHOLD, 0, buf, wrptr - buf);
        if (ret != SR_OK) {
                sr_err("Cannot set threshold voltage %.2fV.", voltage);
                return ret;
        }

        return SR_OK;
}

/*
 * Communicates a channel's configuration to the device after the
 * parameters may have changed. Configuration of one channel may
 * interfere with other channels since they share FPGA registers.
 */
static int set_pwm_config(const struct sr_dev_inst *sdi, size_t idx)
{
        static uint8_t reg_bases[] = { REG_PWM1, REG_PWM2, };

        struct dev_context *devc;
        struct pwm_setting *params;
        uint8_t reg_base;
        double val_f;
        uint32_t val_u;
        uint32_t period, duty;
        size_t ch;
        int ret;
        uint8_t enable_all, enable_cfg, reg_val;
        uint8_t buf[REG_PWM2 - REG_PWM1]; /* Width of one REG_PWMx. */
        uint8_t *wrptr;

        devc = sdi->priv;
        if (idx >= ARRAY_SIZE(devc->pwm_setting))
                return SR_ERR_ARG;
        params = &devc->pwm_setting[idx];
        if (idx >= ARRAY_SIZE(reg_bases))
                return SR_ERR_ARG;
        reg_base = reg_bases[idx];

        /*
         * Map application's specs to hardware register values. Do math
         * in floating point initially, but convert to u32 eventually.
         */
        sr_dbg("PWM config, app spec, ch %zu, en %d, freq %.1f, duty %.1f.",
                idx, params->enabled ? 1 : 0, params->freq, params->duty);
        val_f = PWM_CLOCK;
        val_f /= params->freq;
        val_u = val_f;
        period = val_u;
        val_f = period;
        val_f *= params->duty;
        val_f /= 100.0;
        val_f += 0.5;
        val_u = val_f;
        duty = val_u;
        sr_dbg("PWM config, reg 0x%04x, freq %u, duty %u.",
                (unsigned)reg_base, (unsigned)period, (unsigned)duty);

        /* Get the "enabled" state of all supported PWM channels. */
        enable_all = 0;
        for (ch = 0; ch < ARRAY_SIZE(devc->pwm_setting); ch++) {
                if (!devc->pwm_setting[ch].enabled)
                        continue;
                enable_all |= 1U << ch;
        }
        enable_cfg = 1U << idx;
        sr_spew("PWM config, enable all 0x%02hhx, cfg 0x%02hhx.",
                enable_all, enable_cfg);

        /*
         * Disable the to-get-configured channel before its parameters
         * will change. Or disable and exit when the channel is supposed
         * to get turned off.
         */
        sr_spew("PWM config, disabling before param change.");
        reg_val = enable_all & ~enable_cfg;
        ret = ctrl_out(sdi, CMD_FPGA_SPI, REG_PWM_EN, 0,
                &reg_val, sizeof(reg_val));
        if (ret != SR_OK) {
                sr_err("Cannot adjust PWM enabled state.");
                return ret;
        }
        if (!params->enabled)
                return SR_OK;

        /* Write register values to device. */
        sr_spew("PWM config, sending new parameters.");
        wrptr = buf;
        write_u32le_inc(&wrptr, period);
        write_u32le_inc(&wrptr, duty);
        ret = ctrl_out(sdi, CMD_FPGA_SPI, reg_base, 0, buf, wrptr - buf);
        if (ret != SR_OK) {
                sr_err("Cannot change PWM parameters.");
                return ret;
        }

        /* Enable configured channel after write completion. */
        sr_spew("PWM config, enabling after param change.");
        reg_val = enable_all | enable_cfg;
        ret = ctrl_out(sdi, CMD_FPGA_SPI, REG_PWM_EN, 0,
                &reg_val, sizeof(reg_val));
        if (ret != SR_OK) {
                sr_err("Cannot adjust PWM enabled state.");
                return ret;
        }

        return SR_OK;
}

/*
 * Determine the number of enabled channels as well as their bitmask
 * representation. Derive data here which later simplifies processing
 * of raw capture data memory content in streaming mode.
 */
static void la2016_prepare_stream(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;
        struct stream_state_t *stream;
        size_t channel_mask;
        GSList *l;
        struct sr_channel *ch;

        devc = sdi->priv;
        stream = &devc->stream;
        memset(stream, 0, sizeof(*stream));

        stream->enabled_count = 0;
        for (l = sdi->channels; l; l = l->next) {
                ch = l->data;
                if (ch->type != SR_CHANNEL_LOGIC)
                        continue;
                if (!ch->enabled)
                        continue;
                channel_mask = 1UL << ch->index;
                stream->enabled_mask |= channel_mask;
                stream->channel_masks[stream->enabled_count++] = channel_mask;
        }
        stream->channel_index = 0;
}

/*
 * This routine configures the set of enabled channels, as well as the
 * trigger condition (if one was specified). Also prepares the capture
 * data processing in stream mode, where the memory layout dramatically
 * differs from normal mode.
 */
static int set_trigger_config(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;
        struct sr_trigger *trigger;
        struct trigger_cfg {
                uint32_t channels;      /* Actually: Enabled channels? */
                uint32_t enabled;       /* Actually: Triggering channels? */
                uint32_t level;
                uint32_t high_or_falling;
        } cfg;
        GSList *stages;
        GSList *channel;
        struct sr_trigger_stage *stage1;
        struct sr_trigger_match *match;
        uint32_t ch_mask;
        int ret;
        uint8_t buf[REG_UNKNOWN_30 - REG_TRIGGER]; /* Width of REG_TRIGGER. */
        uint8_t *wrptr;

        devc = sdi->priv;

        la2016_prepare_stream(sdi);

        memset(&cfg, 0, sizeof(cfg));
        cfg.channels = devc->stream.enabled_mask;
        if (!cfg.channels) {
                sr_err("Need at least one enabled logic channel.");
                return SR_ERR_ARG;
        }
        trigger = sr_session_trigger_get(sdi->session);
        if (trigger && trigger->stages) {
                stages = trigger->stages;
                stage1 = stages->data;
                if (stages->next) {
                        sr_err("Only one trigger stage supported for now.");
                        return SR_ERR_ARG;
                }
                channel = stage1->matches;
                while (channel) {
                        match = channel->data;
                        ch_mask = 1UL << match->channel->index;

                        switch (match->match) {
                        case SR_TRIGGER_ZERO:
                                cfg.level |= ch_mask;
                                cfg.high_or_falling &= ~ch_mask;
                                break;
                        case SR_TRIGGER_ONE:
                                cfg.level |= ch_mask;
                                cfg.high_or_falling |= ch_mask;
                                break;
                        case SR_TRIGGER_RISING:
                                if ((cfg.enabled & ~cfg.level)) {
                                        sr_err("Device only supports one edge trigger.");
                                        return SR_ERR_ARG;
                                }
                                cfg.level &= ~ch_mask;
                                cfg.high_or_falling &= ~ch_mask;
                                break;
                        case SR_TRIGGER_FALLING:
                                if ((cfg.enabled & ~cfg.level)) {
                                        sr_err("Device only supports one edge trigger.");
                                        return SR_ERR_ARG;
                                }
                                cfg.level &= ~ch_mask;
                                cfg.high_or_falling |= ch_mask;
                                break;
                        default:
                                sr_err("Unknown trigger condition.");
                                return SR_ERR_ARG;
                        }
                        cfg.enabled |= ch_mask;
                        channel = channel->next;
                }
        }
        sr_dbg("Set trigger config: "
                "enabled-channels 0x%04x, triggering-channels 0x%04x, "
                "level-triggered 0x%04x, high/falling 0x%04x.",
                cfg.channels, cfg.enabled, cfg.level, cfg.high_or_falling);

        /*
         * Don't configure hardware trigger parameters in streaming mode
         * or when the device lacks local memory. Yet the above dump of
         * derived parameters from user specs is considered valueable.
         *
         * TODO Add support for soft triggers when hardware triggers in
         * the device are not used or are not available at all.
         */
        if (!devc->model->memory_bits || devc->continuous) {
                if (!devc->model->memory_bits)
                        sr_dbg("Device without memory. No hardware triggers.");
                else if (devc->continuous)
                        sr_dbg("Streaming mode. No hardware triggers.");
                cfg.enabled = 0;
                cfg.level = 0;
                cfg.high_or_falling = 0;
        }

        devc->trigger_involved = cfg.enabled != 0;

        wrptr = buf;
        write_u32le_inc(&wrptr, cfg.channels);
        write_u32le_inc(&wrptr, cfg.enabled);
        write_u32le_inc(&wrptr, cfg.level);
        write_u32le_inc(&wrptr, cfg.high_or_falling);
        /* TODO
         * Comment on this literal 16. Origin, meaning? Cannot be the
         * register offset, nor the transfer length. Is it a channels
         * count that is relevant for 16 and 32 channel models? Is it
         * an obsolete experiment?
         */
        ret = ctrl_out(sdi, CMD_FPGA_SPI, REG_TRIGGER, 16, buf, wrptr - buf);
        if (ret != SR_OK) {
                sr_err("Cannot setup trigger configuration.");
                return ret;
        }

        return SR_OK;
}

/*
 * This routine communicates the sample configuration to the device:
 * Total samples count and samplerate, pre-trigger configuration.
 */
static int set_sample_config(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;
        uint64_t min_samplerate, eff_samplerate;
        uint64_t stream_bandwidth;
        uint16_t divider_u16;
        uint64_t limit_samples;
        uint64_t pre_trigger_samples;
        uint64_t pre_trigger_memory;
        uint8_t buf[REG_TRIGGER - REG_SAMPLING]; /* Width of REG_SAMPLING. */
        uint8_t *wrptr;
        int ret;

        devc = sdi->priv;

        if (devc->samplerate > devc->model->samplerate) {
                sr_err("Too high a sample rate: %" PRIu64 ".",
                        devc->samplerate);
                return SR_ERR_ARG;
        }
        min_samplerate = devc->model->samplerate;
        min_samplerate /= 65536;
        if (devc->samplerate < min_samplerate) {
                sr_err("Too low a sample rate: %" PRIu64 ".",
                        devc->samplerate);
                return SR_ERR_ARG;
        }
        divider_u16 = devc->model->samplerate / devc->samplerate;
        eff_samplerate = devc->model->samplerate / divider_u16;

        ret = sr_sw_limits_get_remain(&devc->sw_limits,
                &limit_samples, NULL, NULL, NULL);
        if (ret != SR_OK) {
                sr_err("Cannot get acquisition limits.");
                return ret;
        }
        if (limit_samples > LA2016_NUM_SAMPLES_MAX) {
                sr_warn("Too high a sample depth: %" PRIu64 ", capping.",
                        limit_samples);
                limit_samples = LA2016_NUM_SAMPLES_MAX;
        }
        if (limit_samples == 0) {
                limit_samples = LA2016_NUM_SAMPLES_MAX;
                sr_dbg("Passing %" PRIu64 " to HW for unlimited samples.",
                        limit_samples);
        }

        /*
         * The acquisition configuration communicates "pre-trigger"
         * specs in several formats. sigrok users provide a percentage
         * (0-100%), which translates to a pre-trigger samples count
         * (assuming that a total samples count limit was specified).
         * The device supports hardware compression, which depends on
         * slowly changing input data to be effective. Fast changing
         * input data may occupy more space in sample memory than its
         * uncompressed form would. This is why a third parameter can
         * limit the amount of sample memory to use for pre-trigger
         * data. Only the upper 24 bits of that memory size spec get
         * communicated to the device (written to its FPGA register).
         */
        if (!devc->model->memory_bits) {
                sr_dbg("Memory-less device, skipping pre-trigger config.");
                pre_trigger_samples = 0;
                pre_trigger_memory = 0;
        } else if (devc->trigger_involved) {
                pre_trigger_samples = limit_samples;
                pre_trigger_samples *= devc->capture_ratio;
                pre_trigger_samples /= 100;
                pre_trigger_memory = devc->model->memory_bits;
                pre_trigger_memory *= UINT64_C(1024 * 1024 * 1024);
                pre_trigger_memory /= 8; /* devc->model->channel_count ? */
                pre_trigger_memory *= devc->capture_ratio;
                pre_trigger_memory /= 100;
        } else {
                sr_dbg("No trigger setup, skipping pre-trigger config.");
                pre_trigger_samples = 0;
                pre_trigger_memory = 0;
        }
        /* Ensure non-zero value after LSB shift out in HW reg. */
        if (pre_trigger_memory < 0x100)
                pre_trigger_memory = 0x100;

        sr_dbg("Set sample config: %" PRIu64 "kHz (div %" PRIu16 "), %" PRIu64 " samples.",
                eff_samplerate / SR_KHZ(1), divider_u16, limit_samples);
        sr_dbg("Capture ratio %" PRIu64 "%%, count %" PRIu64 ", mem %" PRIu64 ".",
                devc->capture_ratio, pre_trigger_samples, pre_trigger_memory);

        if (devc->continuous) {
                stream_bandwidth = eff_samplerate;
                stream_bandwidth *= devc->stream.enabled_count;
                sr_dbg("Streaming: channel count %zu, product %" PRIu64 ".",
                        devc->stream.enabled_count, stream_bandwidth);
                stream_bandwidth /= 1000 * 1000;
                if (stream_bandwidth >= LA2016_STREAM_MBPS_MAX) {
                        sr_warn("High USB stream bandwidth: %" PRIu64 "Mbps.",
                                stream_bandwidth);
                }
                if (stream_bandwidth < LA2016_STREAM_PUSH_THR) {
                        sr_dbg("Streaming: low Mbps, suggest periodic flush.");
                        devc->stream.flush_period_ms = LA2016_STREAM_PUSH_IVAL;
                }
        }

        /*
         * The acquisition configuration occupies a total of 16 bytes:
         * - A 34bit total samples count limit (up to 10 billions) that
         *   is kept in a 40bit register.
         * - A 34bit pre-trigger samples count limit (up to 10 billions)
         *   in another 40bit register.
         * - A 32bit pre-trigger memory space limit (in bytes) of which
         *   the upper 24bits are kept in an FPGA register.
         * - A 16bit clock divider which gets applied to the maximum
         *   samplerate of the device.
         * - An 8bit register of unknown meaning. Currently always 0.
         */
        wrptr = buf;
        write_u40le_inc(&wrptr, limit_samples);
        write_u40le_inc(&wrptr, pre_trigger_samples);
        write_u24le_inc(&wrptr, pre_trigger_memory >> 8);
        write_u16le_inc(&wrptr, divider_u16);
        write_u8_inc(&wrptr, 0);
        ret = ctrl_out(sdi, CMD_FPGA_SPI, REG_SAMPLING, 0, buf, wrptr - buf);
        if (ret != SR_OK) {
                sr_err("Cannot setup acquisition configuration.");
                return ret;
        }

        return SR_OK;
}

/*
 * FPGA register REG_RUN holds the run state (u16le format). Bit fields
 * of interest:
 *   bit 0: value 1 = idle
 *   bit 1: value 1 = writing to SDRAM
 *   bit 2: value 0 = waiting for trigger, 1 = trigger seen
 *   bit 3: value 0 = pretrigger sampling, 1 = posttrigger sampling
 * The meaning of other bit fields is unknown.
 *
 * Typical values in order of appearance during execution:
 *   0x85e1: idle, no acquisition pending
 *     IDLE set, TRGD don't care, POST don't care; DRAM don't care
 *     "In idle state." Takes precedence over all others.
 *   0x85e2: pre-sampling, samples before the trigger position,
 *     when capture ratio > 0%
 *     IDLE clear, TRGD clear, POST clear; DRAM don't care
 *     "Not idle any more, no post yet, not triggered yet."
 *   0x85ea: pre-sampling complete, now waiting for the trigger
 *     (whilst sampling continuously)
 *     IDLE clear, TRGD clear, POST set; DRAM don't care
 *     "Post set thus after pre, not triggered yet"
 *   0x85ee: trigger seen, capturing post-trigger samples, running
 *     IDLE clear, TRGD set, POST set; DRAM don't care
 *     "Triggered and in post, not idle yet."
 *   0x85ed: idle
 *     IDLE set, TRGD don't care, POST don't care; DRAM don't care
 *     "In idle state." TRGD/POST don't care, same meaning as above.
 */
static const uint16_t runstate_mask_idle = RUNSTATE_IDLE_BIT;
static const uint16_t runstate_patt_idle = RUNSTATE_IDLE_BIT;
static const uint16_t runstate_mask_step =
        RUNSTATE_IDLE_BIT | RUNSTATE_TRGD_BIT | RUNSTATE_POST_BIT;
static const uint16_t runstate_patt_pre_trig = 0;
static const uint16_t runstate_patt_wait_trig = RUNSTATE_POST_BIT;
static const uint16_t runstate_patt_post_trig =
        RUNSTATE_TRGD_BIT | RUNSTATE_POST_BIT;

static uint16_t run_state(const struct sr_dev_inst *sdi)
{
        static uint16_t previous_state;

        int ret;
        uint16_t state;
        uint8_t buff[REG_PWM_EN - REG_RUN]; /* Width of REG_RUN. */
        const uint8_t *rdptr;
        const char *label;

        ret = ctrl_in(sdi, CMD_FPGA_SPI, REG_RUN, 0, buff, sizeof(state));
        if (ret != SR_OK) {
                sr_err("Cannot read run state.");
                return ret;
        }
        rdptr = buff;
        state = read_u16le_inc(&rdptr);

        /*
         * Avoid flooding the log, only dump values as they change.
         * The routine is called about every 50ms.
         */
        if (state == previous_state)
                return state;

        previous_state = state;
        label = NULL;
        if ((state & runstate_mask_idle) == runstate_patt_idle)
                label = "idle";
        if ((state & runstate_mask_step) == runstate_patt_pre_trig)
                label = "pre-trigger sampling";
        if ((state & runstate_mask_step) == runstate_patt_wait_trig)
                label = "sampling, waiting for trigger";
        if ((state & runstate_mask_step) == runstate_patt_post_trig)
                label = "post-trigger sampling";
        if (label && *label)
                sr_dbg("Run state: 0x%04x (%s).", state, label);
        else
                sr_dbg("Run state: 0x%04x.", state);

        return state;
}

static gboolean la2016_is_idle(const struct sr_dev_inst *sdi)
{
        uint16_t state;

        state = run_state(sdi);
        if ((state & runstate_mask_idle) == runstate_patt_idle)
                return TRUE;

        return FALSE;
}

static int set_run_mode(const struct sr_dev_inst *sdi, uint8_t mode)
{
        int ret;

        ret = ctrl_out(sdi, CMD_FPGA_SPI, REG_RUN, 0, &mode, sizeof(mode));
        if (ret != SR_OK) {
                sr_err("Cannot configure run mode %d.", mode);
                return ret;
        }

        return SR_OK;
}

static int get_capture_info(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;
        int ret;
        uint8_t buf[REG_TRIGGER - REG_SAMPLING]; /* Width of REG_SAMPLING. */
        const uint8_t *rdptr;

        devc = sdi->priv;

        ret = ctrl_in(sdi, CMD_FPGA_SPI, REG_SAMPLING, 0, buf, sizeof(buf));
        if (ret != SR_OK) {
                sr_err("Cannot read capture info.");
                return ret;
        }

        rdptr = buf;
        devc->info.n_rep_packets = read_u32le_inc(&rdptr);
        devc->info.n_rep_packets_before_trigger = read_u32le_inc(&rdptr);
        devc->info.write_pos = read_u32le_inc(&rdptr);

        sr_dbg("Capture info: n_rep_packets: 0x%08x/%d, before_trigger: 0x%08x/%d, write_pos: 0x%08x/%d.",
                devc->info.n_rep_packets, devc->info.n_rep_packets,
                devc->info.n_rep_packets_before_trigger,
                devc->info.n_rep_packets_before_trigger,
                devc->info.write_pos, devc->info.write_pos);

        if (devc->info.n_rep_packets % devc->packets_per_chunk) {
                sr_warn("Unexpected packets count %lu, not a multiple of %lu.",
                        (unsigned long)devc->info.n_rep_packets,
                        (unsigned long)devc->packets_per_chunk);
        }

        return SR_OK;
}

SR_PRIV int la2016_upload_firmware(const struct sr_dev_inst *sdi,
        struct sr_context *sr_ctx, libusb_device *dev, gboolean skip_upload)
{
        struct dev_context *devc;
        uint16_t pid;
        char *fw;
        int ret;

        devc = sdi ? sdi->priv : NULL;
        if (!devc || !devc->usb_pid)
                return SR_ERR_ARG;
        pid = devc->usb_pid;

        fw = g_strdup_printf(MCU_FWFILE_FMT, pid);
        sr_info("USB PID %04hx, MCU firmware '%s'.", pid, fw);
        devc->mcu_firmware = g_strdup(fw);

        if (skip_upload)
                ret = SR_OK;
        else
                ret = ezusb_upload_firmware(sr_ctx, dev, USB_CONFIGURATION, fw);
        g_free(fw);
        if (ret != SR_OK)
                return ret;

        return SR_OK;
}

static void LIBUSB_CALL receive_transfer(struct libusb_transfer *xfer);

static void la2016_usbxfer_release_cb(gpointer p)
{
        struct libusb_transfer *xfer;

        xfer = p;
        g_free(xfer->buffer);
        libusb_free_transfer(xfer);
}

static int la2016_usbxfer_release(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;

        devc = sdi ? sdi->priv : NULL;
        if (!devc)
                return SR_ERR_ARG;

        /* Release all USB transfers. */
        g_slist_free_full(devc->transfers, la2016_usbxfer_release_cb);
        devc->transfers = NULL;

        return SR_OK;
}

static int la2016_usbxfer_allocate(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;
        size_t bufsize, xfercount;
        uint8_t *buffer;
        struct libusb_transfer *xfer;

        devc = sdi ? sdi->priv : NULL;
        if (!devc)
                return SR_ERR_ARG;

        /* Transfers were already allocated before? */
        if (devc->transfers)
                return SR_OK;

        /*
         * Allocate all USB transfers and their buffers. Arrange for a
         * buffer size which is within the device's capabilities, and
         * is a multiple of the USB endpoint's size, to make use of the
         * RAW_IO performance feature.
         *
         * Implementation detail: The LA2016_USB_BUFSZ value happens
         * to match all those constraints. No additional arithmetics is
         * required in this location.
         */
        bufsize = LA2016_USB_BUFSZ;
        xfercount = LA2016_USB_XFER_COUNT;
        while (xfercount--) {
                buffer = g_try_malloc(bufsize);
                if (!buffer) {
                        sr_err("Cannot allocate USB transfer buffer.");
                        return SR_ERR_MALLOC;
                }
                xfer = libusb_alloc_transfer(0);
                if (!xfer) {
                        sr_err("Cannot allocate USB transfer.");
                        g_free(buffer);
                        return SR_ERR_MALLOC;
                }
                xfer->buffer = buffer;
                devc->transfers = g_slist_append(devc->transfers, xfer);
        }
        devc->transfer_bufsize = bufsize;

        return SR_OK;
}

static int la2016_usbxfer_cancel_all(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;
        GSList *l;
        struct libusb_transfer *xfer;

        devc = sdi ? sdi->priv : NULL;
        if (!devc)
                return SR_ERR_ARG;

        /* Unconditionally cancel the transfer. Ignore errors. */
        for (l = devc->transfers; l; l = l->next) {
                xfer = l->data;
                if (!xfer)
                        continue;
                libusb_cancel_transfer(xfer);
        }

        return SR_OK;
}

static int la2016_usbxfer_resubmit(const struct sr_dev_inst *sdi,
        struct libusb_transfer *xfer)
{
        struct dev_context *devc;
        struct sr_usb_dev_inst *usb;
        libusb_transfer_cb_fn cb;
        int ret;

        devc = sdi ? sdi->priv : NULL;
        usb = sdi ? sdi->conn : NULL;
        if (!devc || !usb)
                return SR_ERR_ARG;

        if (!xfer)
                return SR_ERR_ARG;

        cb = receive_transfer;
        libusb_fill_bulk_transfer(xfer, usb->devhdl,
                USB_EP_CAPTURE_DATA | LIBUSB_ENDPOINT_IN,
                xfer->buffer, devc->transfer_bufsize,
                cb, (void *)sdi, CAPTURE_TIMEOUT_MS);
        ret = libusb_submit_transfer(xfer);
        if (ret != 0) {
                sr_err("Cannot submit USB transfer: %s.",
                        libusb_error_name(ret));
                return SR_ERR_IO;
        }

        return SR_OK;
}

static int la2016_usbxfer_submit_all(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;
        GSList *l;
        struct libusb_transfer *xfer;
        int ret;

        devc = sdi ? sdi->priv : NULL;
        if (!devc)
                return SR_ERR_ARG;

        for (l = devc->transfers; l; l = l->next) {
                xfer = l->data;
                if (!xfer)
                        return SR_ERR_ARG;
                ret = la2016_usbxfer_resubmit(sdi, xfer);
                if (ret != SR_OK)
                        return ret;
        }

        return SR_OK;
}

SR_PRIV int la2016_setup_acquisition(const struct sr_dev_inst *sdi,
        double voltage)
{
        struct dev_context *devc;
        int ret;
        uint8_t cmd;

        devc = sdi->priv;

        ret = set_threshold_voltage(sdi, voltage);
        if (ret != SR_OK)
                return ret;

        cmd = devc->continuous ? CAPTMODE_STREAM : CAPTMODE_TO_RAM;
        ret = ctrl_out(sdi, CMD_FPGA_SPI, REG_CAPT_MODE, 0, &cmd, sizeof(cmd));
        if (ret != SR_OK) {
                sr_err("Cannot send command to stop sampling.");
                return ret;
        }

        ret = set_trigger_config(sdi);
        if (ret != SR_OK)
                return ret;

        ret = set_sample_config(sdi);
        if (ret != SR_OK)
                return ret;

        return SR_OK;
}

SR_PRIV int la2016_start_acquisition(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;
        int ret;

        devc = sdi->priv;

        ret = la2016_usbxfer_allocate(sdi);
        if (ret != SR_OK)
                return ret;

        if (devc->continuous) {
                ret = ctrl_out(sdi, CMD_BULK_RESET, 0x00, 0, NULL, 0);
                if (ret != SR_OK)
                        return ret;

                ret = la2016_usbxfer_submit_all(sdi);
                if (ret != SR_OK)
                        return ret;

                /*
                 * Periodic receive callback will set runmode. This
                 * activity MUST be close to data reception, a pause
                 * between these steps breaks the stream's operation.
                 */
        } else {
                ret = set_run_mode(sdi, RUNMODE_RUN);
                if (ret != SR_OK)
                        return ret;
        }

        return SR_OK;
}

static int la2016_stop_acquisition(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;
        int ret;

        ret = set_run_mode(sdi, RUNMODE_HALT);
        if (ret != SR_OK)
                return ret;

        devc = sdi->priv;
        if (devc->continuous)
                devc->download_finished = TRUE;

        return SR_OK;
}

SR_PRIV int la2016_abort_acquisition(const struct sr_dev_inst *sdi)
{
        int ret;

        ret = la2016_stop_acquisition(sdi);
        if (ret != SR_OK)
                return ret;

        (void)la2016_usbxfer_cancel_all(sdi);

        return SR_OK;
}

static int la2016_start_download(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;
        int ret;
        uint8_t wrbuf[REG_SAMPLING - REG_BULK]; /* Width of REG_BULK. */
        uint8_t *wrptr;

        devc = sdi->priv;

        ret = get_capture_info(sdi);
        if (ret != SR_OK)
                return ret;

        devc->n_transfer_packets_to_read = devc->info.n_rep_packets;
        devc->n_transfer_packets_to_read /= devc->packets_per_chunk;
        devc->n_bytes_to_read = devc->n_transfer_packets_to_read;
        devc->n_bytes_to_read *= TRANSFER_PACKET_LENGTH;
        devc->read_pos = devc->info.write_pos - devc->n_bytes_to_read;
        devc->n_reps_until_trigger = devc->info.n_rep_packets_before_trigger;

        sr_dbg("Want to read %u xfer-packets starting from pos %" PRIu32 ".",
                devc->n_transfer_packets_to_read, devc->read_pos);

        ret = ctrl_out(sdi, CMD_BULK_RESET, 0x00, 0, NULL, 0);
        if (ret != SR_OK) {
                sr_err("Cannot reset USB bulk state.");
                return ret;
        }
        sr_dbg("Will read from 0x%08lx, 0x%08x bytes.",
                (unsigned long)devc->read_pos, devc->n_bytes_to_read);
        wrptr = wrbuf;
        write_u32le_inc(&wrptr, devc->read_pos);
        write_u32le_inc(&wrptr, devc->n_bytes_to_read);
        ret = ctrl_out(sdi, CMD_FPGA_SPI, REG_BULK, 0, wrbuf, wrptr - wrbuf);
        if (ret != SR_OK) {
                sr_err("Cannot send USB bulk config.");
                return ret;
        }

        ret = la2016_usbxfer_submit_all(sdi);
        if (ret != SR_OK) {
                sr_err("Cannot submit USB bulk transfers.");
                return ret;
        }

        ret = ctrl_out(sdi, CMD_BULK_START, 0x00, 0, NULL, 0);
        if (ret != SR_OK) {
                sr_err("Cannot start USB bulk transfers.");
                return ret;
        }

        return SR_OK;
}

/*
 * A chunk (received via USB) contains a number of transfers (USB length
 * divided by 16) which contain a number of packets (5 per transfer) which
 * contain a number of samples (8bit repeat count per 16bit sample data).
 */
static void send_chunk(struct sr_dev_inst *sdi,
        const uint8_t *data_buffer, size_t data_length)
{
        struct dev_context *devc;
        size_t num_xfers, num_pkts;
        const uint8_t *rp;
        uint32_t sample_value;
        size_t repetitions;
        uint8_t sample_buff[sizeof(sample_value)];

        devc = sdi->priv;

        /* Ignore incoming USB data after complete sample data download. */
        if (devc->download_finished)
                return;

        if (devc->trigger_involved && !devc->trigger_marked && devc->info.n_rep_packets_before_trigger == 0) {
                feed_queue_logic_send_trigger(devc->feed_queue);
                devc->trigger_marked = TRUE;
        }

        /*
         * Adjust the number of remaining bytes to read from the device
         * before the processing of the currently received chunk affects
         * the variable which holds the number of received bytes.
         */
        if (data_length > devc->n_bytes_to_read)
                devc->n_bytes_to_read = 0;
        else
                devc->n_bytes_to_read -= data_length;

        /* Process the received chunk of capture data. */
        sample_value = 0;
        rp = data_buffer;
        num_xfers = data_length / TRANSFER_PACKET_LENGTH;
        while (num_xfers--) {
                num_pkts = devc->packets_per_chunk;
                while (num_pkts--) {

                        /* TODO Verify 32channel layout. */
                        if (devc->model->channel_count == 32)
                                sample_value = read_u32le_inc(&rp);
                        else if (devc->model->channel_count == 16)
                                sample_value = read_u16le_inc(&rp);
                        repetitions = read_u8_inc(&rp);

                        devc->total_samples += repetitions;

                        write_u32le(sample_buff, sample_value);
                        feed_queue_logic_submit(devc->feed_queue,
                                sample_buff, repetitions);
                        sr_sw_limits_update_samples_read(&devc->sw_limits,
                                repetitions);

                        if (devc->trigger_involved && !devc->trigger_marked) {
                                if (!--devc->n_reps_until_trigger) {
                                        feed_queue_logic_send_trigger(devc->feed_queue);
                                        devc->trigger_marked = TRUE;
                                        sr_dbg("Trigger position after %" PRIu64 " samples, %.6fms.",
                                                devc->total_samples,
                                                (double)devc->total_samples / devc->samplerate * 1e3);
                                }
                        }
                }
                (void)read_u8_inc(&rp); /* Skip sequence number. */
        }

        /*
         * Check for several conditions which shall terminate the
         * capture data download: When the amount of capture data in
         * the device is exhausted. When the user specified samples
         * count limit is reached.
         */
        if (!devc->n_bytes_to_read) {
                devc->download_finished = TRUE;
        } else {
                sr_dbg("%" PRIu32 " more bytes to download from the device.",
                        devc->n_bytes_to_read);
        }
        if (!devc->download_finished && sr_sw_limits_check(&devc->sw_limits)) {
                sr_dbg("Acquisition limit reached.");
                devc->download_finished = TRUE;
        }
        if (devc->download_finished) {
                sr_dbg("Download finished, flushing session feed queue.");
                feed_queue_logic_flush(devc->feed_queue);
        }
        sr_dbg("Total samples after chunk: %" PRIu64 ".", devc->total_samples);
}

/*
 * Process a chunk of capture data in streaming mode. The memory layout
 * is rather different from "normal mode" (see the send_chunk() routine
 * above). In streaming mode data is not compressed, and memory cells
 * neither contain raw sampled pin values at a given point in time. The
 * memory content needs transformation.
 * - The memory content can be seen as a sequence of memory cells.
 * - Each cell contains samples that correspond to the same channel.
 *   The next cell contains samples for the next channel, etc.
 * - Only enabled channels occupy memory cells. Disabled channels are
 *   not part of the capture data memory layout.
 * - The LSB bit position in a cell is the sample which was taken first
 *   for this channel. Upper bit positions were taken later.
 *
 * Implementor's note: This routine is inspired by convert_sample_data()
 * in the https://github.com/AlexUg/sigrok implementation. Which in turn
 * appears to have been derived from the saleae-logic16 sigrok driver.
 * The code is phrased conservatively to verify the layout as discussed
 * above, performance was not a priority. Operation was verified with an
 * LA2016 device. The memory layout of 32 channel models is yet to get
 * determined.
 */
static void stream_data(struct sr_dev_inst *sdi,
        const uint8_t *data_buffer, size_t data_length)
{
        struct dev_context *devc;
        struct stream_state_t *stream;
        size_t bit_count;
        const uint8_t *rp;
        uint32_t sample_value;
        uint8_t sample_buff[sizeof(sample_value)];
        size_t bit_idx;
        uint32_t ch_mask;

        devc = sdi->priv;
        stream = &devc->stream;

        /* Ignore incoming USB data after complete sample data download. */
        if (devc->download_finished)
                return;
        sr_dbg("Stream mode, got another chunk: %p, length %zu.",
                data_buffer, data_length);

        /* TODO Add soft trigger support when in stream mode? */

        /*
         * TODO Are memory cells always as wide as the channel count?
         * Are they always 16bits wide? Verify for 32 channel devices.
         */
        bit_count = devc->model->channel_count;
        if (bit_count == 32) {
                data_length /= sizeof(uint32_t);
        } else if (bit_count == 16) {
                data_length /= sizeof(uint16_t);
        } else {
                /*
                 * Unhandled case. Acquisition should not start.
                 * The statement silences the compiler.
                 */
                return;
        }
        rp = data_buffer;
        sample_value = 0;
        while (data_length--) {
                /* Get another entity. */
                if (bit_count == 32)
                        sample_value = read_u32le_inc(&rp);
                else if (bit_count == 16)
                        sample_value = read_u16le_inc(&rp);

                /* Map the entity's bits to a channel's samples. */
                ch_mask = stream->channel_masks[stream->channel_index];
                for (bit_idx = 0; bit_idx < bit_count; bit_idx++) {
                        if (sample_value & (1UL << bit_idx))
                                stream->sample_data[bit_idx] |= ch_mask;
                }

                /*
                 * Advance to the next channel. Submit a block of
                 * samples when all channels' data was seen.
                 */
                stream->channel_index++;
                if (stream->channel_index != stream->enabled_count)
                        continue;
                for (bit_idx = 0; bit_idx < bit_count; bit_idx++) {
                        sample_value = stream->sample_data[bit_idx];
                        write_u32le(sample_buff, sample_value);
                        feed_queue_logic_submit(devc->feed_queue, sample_buff, 1);
                }
                sr_sw_limits_update_samples_read(&devc->sw_limits, bit_count);
                devc->total_samples += bit_count;
                memset(stream->sample_data, 0, sizeof(stream->sample_data));
                stream->channel_index = 0;
        }

        /*
         * Need we count empty or failed USB transfers? This version
         * doesn't, assumes that timeouts are perfectly legal because
         * transfers are started early, and slow samplerates or trigger
         * support in hardware are plausible causes for empty transfers.
         *
         * TODO Maybe a good condition would be (rather large) a timeout
         * after a previous capture data chunk was seen? So that stalled
         * streaming gets detected which _is_ an exceptional condition.
         * We have observed these when "runmode" is set early but bulk
         * transfers start late with a pause after setting the runmode.
         */
        if (sr_sw_limits_check(&devc->sw_limits)) {
                sr_dbg("Acquisition end reached (sw limits).");
                devc->download_finished = TRUE;
        }
        if (devc->download_finished) {
                sr_dbg("Stream receive done, flushing session feed queue.");
                feed_queue_logic_flush(devc->feed_queue);
        }
        sr_dbg("Total samples after chunk: %" PRIu64 ".", devc->total_samples);
}

static void LIBUSB_CALL receive_transfer(struct libusb_transfer *transfer)
{
        struct sr_dev_inst *sdi;
        struct dev_context *devc;
        gboolean was_cancelled, device_gone;
        int ret;

        sdi = transfer->user_data;
        devc = sdi->priv;

        was_cancelled = transfer->status == LIBUSB_TRANSFER_CANCELLED;
        device_gone = transfer->status == LIBUSB_TRANSFER_NO_DEVICE;
        sr_dbg("receive_transfer(): status %s received %d bytes.",
                libusb_error_name(transfer->status), transfer->actual_length);
        if (device_gone) {
                sr_warn("Lost communication to USB device.");
                devc->download_finished = TRUE;
                return;
        }

        /*
         * Implementation detail: A USB transfer timeout is not fatal
         * here. We just process whatever was received, empty input is
         * perfectly acceptable. Reaching (or exceeding) the sw limits
         * or exhausting the device's captured data will complete the
         * sample data download.
         */
        if (devc->continuous)
                stream_data(sdi, transfer->buffer, transfer->actual_length);
        else
                send_chunk(sdi, transfer->buffer, transfer->actual_length);

        /*
         * Re-submit completed transfers (regardless of timeout or
         * data reception), unless the transfer was cancelled when
         * the acquisition was terminated or has completed.
         */
        if (!was_cancelled && !devc->download_finished) {
                ret = la2016_usbxfer_resubmit(sdi, transfer);
                if (ret == SR_OK)
                        return;
                devc->download_finished = TRUE;
        }
}

SR_PRIV int la2016_receive_data(int fd, int revents, void *cb_data)
{
        const struct sr_dev_inst *sdi;
        struct dev_context *devc;
        struct drv_context *drvc;
        struct timeval tv;
        int ret;

        (void)fd;
        (void)revents;

        sdi = cb_data;
        devc = sdi->priv;
        drvc = sdi->driver->context;

        /* Arrange for the start of stream mode when requested. */
        if (devc->continuous && !devc->frame_begin_sent) {
                sr_dbg("First receive callback in stream mode.");
                devc->download_finished = FALSE;
                devc->trigger_marked = FALSE;
                devc->total_samples = 0;

                std_session_send_df_frame_begin(sdi);
                devc->frame_begin_sent = TRUE;

                ret = set_run_mode(sdi, RUNMODE_RUN);
                if (ret != SR_OK) {
                        sr_err("Cannot set 'runmode' to 'run'.");
                        return FALSE;
                }

                ret = ctrl_out(sdi, CMD_BULK_START, 0x00, 0, NULL, 0);
                if (ret != SR_OK) {
                        sr_err("Cannot start USB bulk transfers.");
                        return FALSE;
                }
                sr_dbg("Stream data reception initiated.");
        }

        /*
         * Wait for the acquisition to complete in hardware.
         * Periodically check a potentially configured msecs timeout.
         */
        if (!devc->continuous && !devc->completion_seen) {
                if (!la2016_is_idle(sdi)) {
                        if (sr_sw_limits_check(&devc->sw_limits)) {
                                devc->sw_limits.limit_msec = 0;
                                sr_dbg("Limit reached. Stopping acquisition.");
                                la2016_stop_acquisition(sdi);
                        }
                        /* Not yet ready for sample data download. */
                        return TRUE;
                }
                sr_dbg("Acquisition completion seen (hardware).");
                devc->sw_limits.limit_msec = 0;
                devc->completion_seen = TRUE;
                devc->download_finished = FALSE;
                devc->trigger_marked = FALSE;
                devc->total_samples = 0;

                la2016_dump_fpga_registers(sdi, "acquisition complete", 0, 0);

                /* Initiate the download of acquired sample data. */
                std_session_send_df_frame_begin(sdi);
                devc->frame_begin_sent = TRUE;
                ret = la2016_start_download(sdi);
                if (ret != SR_OK) {
                        sr_err("Cannot start acquisition data download.");
                        return FALSE;
                }
                sr_dbg("Acquisition data download started.");

                return TRUE;
        }

        /* Handle USB reception. Drives sample data download. */
        memset(&tv, 0, sizeof(tv));
        libusb_handle_events_timeout(drvc->sr_ctx->libusb_ctx, &tv);

        /*
         * Periodically flush acquisition data in streaming mode.
         * Without this nudge, previously received and accumulated data
         * keeps sitting in queues and is not seen by applications.
         */
        if (devc->continuous && devc->stream.flush_period_ms) {
                uint64_t now, elapsed;
                now = g_get_monotonic_time();
                if (!devc->stream.last_flushed)
                        devc->stream.last_flushed = now;
                elapsed = now - devc->stream.last_flushed;
                elapsed /= 1000;
                if (elapsed >= devc->stream.flush_period_ms) {
                        sr_dbg("Stream mode, flushing.");
                        feed_queue_logic_flush(devc->feed_queue);
                        devc->stream.last_flushed = now;
                }
        }

        /* Postprocess completion of sample data download. */
        if (devc->download_finished) {
                sr_dbg("Download finished, post processing.");

                la2016_stop_acquisition(sdi);
                usb_source_remove(sdi->session, drvc->sr_ctx);

                la2016_usbxfer_cancel_all(sdi);
                memset(&tv, 0, sizeof(tv));
                libusb_handle_events_timeout(drvc->sr_ctx->libusb_ctx, &tv);

                feed_queue_logic_flush(devc->feed_queue);
                feed_queue_logic_free(devc->feed_queue);
                devc->feed_queue = NULL;
                if (devc->frame_begin_sent) {
                        std_session_send_df_frame_end(sdi);
                        devc->frame_begin_sent = FALSE;
                }
                std_session_send_df_end(sdi);

                sr_dbg("Download finished, done post processing.");
        }

        return TRUE;
}

SR_PRIV int la2016_identify_device(const struct sr_dev_inst *sdi,
        gboolean show_message)
{
        struct dev_context *devc;
        uint8_t buf[8]; /* Larger size of manuf date and device type magic. */
        size_t rdoff, rdlen;
        const uint8_t *rdptr;
        uint8_t date_yy, date_mm;
        uint8_t dinv_yy, dinv_mm;
        uint8_t magic;
        size_t model_idx;
        const struct kingst_model *model;
        int ret;

        devc = sdi->priv;

        /*
         * Four EEPROM bytes at offset 0x20 are the manufacturing date,
         * year and month in BCD format, followed by inverted values for
         * consistency checks. For example bytes 20 04 df fb translate
         * to 2020-04. This information can help identify the vintage of
         * devices when unknown magic numbers are seen.
         */
        rdoff = 0x20;
        rdlen = 4 * sizeof(uint8_t);
        ret = ctrl_in(sdi, CMD_EEPROM, rdoff, 0, buf, rdlen);
        if (ret != SR_OK && !show_message) {
                /* Non-fatal weak attempt during probe. Not worth logging. */
                sr_dbg("Cannot access EEPROM.");
                return SR_ERR_IO;
        } else if (ret != SR_OK) {
                /* Failed attempt in regular use. Non-fatal. Worth logging. */
                sr_err("Cannot read manufacture date in EEPROM.");
        } else {
                if (sr_log_loglevel_get() >= SR_LOG_SPEW) {
                        GString *txt;
                        txt = sr_hexdump_new(buf, rdlen);
                        sr_spew("Manufacture date bytes %s.", txt->str);
                        sr_hexdump_free(txt);
                }
                rdptr = &buf[0];
                date_yy = read_u8_inc(&rdptr);
                date_mm = read_u8_inc(&rdptr);
                dinv_yy = read_u8_inc(&rdptr);
                dinv_mm = read_u8_inc(&rdptr);
                sr_info("Manufacture date: 20%02hx-%02hx.", date_yy, date_mm);
                if ((date_mm ^ dinv_mm) != 0xff || (date_yy ^ dinv_yy) != 0xff)
                        sr_warn("Manufacture date fails checksum test.");
        }

        /*
         * Several Kingst logic analyzer devices share the same USB VID
         * and PID. The product ID determines which MCU firmware to load.
         * The MCU firmware provides access to EEPROM content which then
         * allows to identify the device model. Which in turn determines
         * which FPGA bitstream to load. Eight bytes at offset 0x08 are
         * to get inspected.
         *
         * EEPROM content for model identification is kept redundantly
         * in memory. The values are stored in verbatim and in inverted
         * form, multiple copies are kept at different offsets. Example
         * data:
         *
         *   magic 0x08
         *    | ~magic 0xf7
         *    | |
         *   08f7000008f710ef
         *            | |
         *            | ~magic backup
         *            magic backup
         *
         * Exclusively inspecting the magic byte appears to be sufficient,
         * other fields seem to be 'don't care'.
         *
         *   magic 2 == LA2016 using "kingst-la2016-fpga.bitstream"
         *   magic 3 == LA1016 using "kingst-la1016-fpga.bitstream"
         *   magic 8 == LA2016a using "kingst-la2016a1-fpga.bitstream"
         *              (latest v1.3.0 PCB, perhaps others)
         *   magic 9 == LA1016a using "kingst-la1016a1-fpga.bitstream"
         *              (latest v1.3.0 PCB, perhaps others)
         *
         * When EEPROM content does not match the hardware configuration
         * (the board layout), the software may load but yield incorrect
         * results (like swapped channels). The FPGA bitstream itself
         * will authenticate with IC U10 and fail when its capabilities
         * do not match the hardware model. An LA1016 won't become a
         * LA2016 by faking its EEPROM content.
         */
        devc->identify_magic = 0;
        rdoff = 0x08;
        rdlen = 8 * sizeof(uint8_t);
        ret = ctrl_in(sdi, CMD_EEPROM, rdoff, 0, &buf, rdlen);
        if (ret != SR_OK) {
                sr_err("Cannot read EEPROM device identifier bytes.");
                return ret;
        }
        if (sr_log_loglevel_get() >= SR_LOG_SPEW) {
                GString *txt;
                txt = sr_hexdump_new(buf, rdlen);
                sr_spew("EEPROM magic bytes %s.", txt->str);
                sr_hexdump_free(txt);
        }
        if ((buf[0] ^ buf[1]) == 0xff) {
                /* Primary copy of magic passes complement check. */
                magic = buf[0];
                sr_dbg("Using primary magic, value %d.", (int)magic);
        } else if ((buf[4] ^ buf[5]) == 0xff) {
                /* Backup copy of magic passes complement check. */
                magic = buf[4];
                sr_dbg("Using backup magic, value %d.", (int)magic);
        } else {
                sr_err("Cannot find consistent device type identification.");
                magic = 0;
        }
        devc->identify_magic = magic;

        devc->model = NULL;
        for (model_idx = 0; model_idx < ARRAY_SIZE(models); model_idx++) {
                model = &models[model_idx];
                if (model->magic != magic)
                        continue;
                devc->model = model;
                sr_info("Model '%s', %zu channels, max %" PRIu64 "MHz.",
                        model->name, model->channel_count,
                        model->samplerate / SR_MHZ(1));
                devc->fpga_bitstream = g_strdup_printf(FPGA_FWFILE_FMT,
                        model->fpga_stem);
                sr_info("FPGA bitstream file '%s'.", devc->fpga_bitstream);
                break;
        }
        if (!devc->model) {
                sr_err("Cannot identify as one of the supported models.");
                return SR_ERR_DATA;
        }

        return SR_OK;
}

SR_PRIV int la2016_init_hardware(const struct sr_dev_inst *sdi)
{
        struct dev_context *devc;
        const char *bitstream_fn;
        int ret;
        uint16_t state;

        devc = sdi->priv;
        bitstream_fn = devc ? devc->fpga_bitstream : "";

        ret = check_fpga_bitstream(sdi);
        if (ret != SR_OK) {
                ret = upload_fpga_bitstream(sdi, bitstream_fn);
                if (ret != SR_OK) {
                        sr_err("Cannot upload FPGA bitstream.");
                        return ret;
                }
        }
        ret = enable_fpga_bitstream(sdi);
        if (ret != SR_OK) {
                sr_err("Cannot enable FPGA bitstream after upload.");
                return ret;
        }

        state = run_state(sdi);
        if ((state & 0xfff0) != 0x85e0) {
                sr_warn("Unexpected run state, want 0x85eX, got 0x%04x.", state);
        }

        ret = ctrl_out(sdi, CMD_BULK_RESET, 0x00, 0, NULL, 0);
        if (ret != SR_OK) {
                sr_err("Cannot reset USB bulk transfer.");
                return ret;
        }

        sr_dbg("Device should be initialized.");

        return SR_OK;
}

SR_PRIV int la2016_deinit_hardware(const struct sr_dev_inst *sdi)
{
        int ret;

        ret = ctrl_out(sdi, CMD_FPGA_ENABLE, 0x00, 0, NULL, 0);
        if (ret != SR_OK) {
                sr_err("Cannot deinitialize device's FPGA.");
                return ret;
        }

        return SR_OK;
}

SR_PRIV void la2016_release_resources(const struct sr_dev_inst *sdi)
{
        (void)la2016_usbxfer_release(sdi);
}

SR_PRIV int la2016_write_pwm_config(const struct sr_dev_inst *sdi, size_t idx)
{
        return set_pwm_config(sdi, idx);
}